Fuel injection system

ABSTRACT

There is well known that the more the timing of fuel injection is advanced, the more the start ability of an engine is improved. However, with regard to the conventional fuel injection system, when a stopping process of the engine is performed, a timer piston determining timing of fuel injection remains at a position at which the piston exists at the time that the stopping process is performed. Then, at the time of next starting of the engine, the timer piston does not often exist in the advanced angle side and the start ability may be poor. For solving this problem, an engine control module (ECM)  21  advances a timer piston  52  and stops fuel injection of a fuel injection pump  40  at the time that actual phase difference C reaches stopping target phase difference Z so as to stop an engine  20.

TECHNICAL FIELD

The present invention relates to a fuel injection system. Moreparticularly, the present invention relates to a fuel injection systemwhich comprises a control means controlling timing of fuel injection toa cylinder of an engine and drivingly controls a rack adjusting fuelinjection amount.

BACKGROUND ART

The conventional diesel engine is driven while the phase differencebetween the phase of a camshaft, which is the drive source of fuelinjection of a fuel injection pump and determines timing of fuelinjection, and the phase of a crankshaft of the engine is kept at acertain value.

By changing the phase difference forward or rearward following the stateof the engine, the engine can be driven efficiently.

As a device changing phase of the camshaft of the fuel injection pump,there is well known a hydraulic timer unit. An example thereof is shownin below patent literature 1.

The hydraulic timer unit comprises a timer piston (it is also referredto as “shuttle piston”) between a camshaft coupling fixed to thecamshaft of the fuel injection pump and a pump driving gear to whichrotation of the crankshaft is transmitted so as to change the phaseangle of the shafts.

The timer piston spline-fits the outer peripheral surface of thecamshaft coupling straightly, and a pump driving gear spline-fits theouter peripheral surface of the timer piston helically.

According to this construction, the phase difference between thecamshaft coupling and the pump driving gear can be changed by slidingthe timer piston along the spline direction of the camshaft coupling.

This slide of the timer piston is performed by oil pressure, and the oilpressure is controlled by an Engine Control Module (ECM) which controlsthe engine.

Accordingly, the ECM controls the timer piston to the advanced side orthe retarded side following the state of the engine so as to make thetiming of fuel injection pertinent.

Now, with regard to such a fuel injection system that is describedabove, an engine stopping process is performed for example that anoperator performs a stopping operation with an operation part such as akey switch, and then the ECM stops fuel injection to the engine so as tostop the engine.

Conventionally, in this stopping process, the timer piston is stopped ata position at which the piston exists at the time that the operatorperforms the stopping operation or a position at which the piston existsat the time that fuel injection is stopped.

Namely, the timer piston remains at the position of normal driving ofthe engine.

The timer piston is generally controlled hydraulically, whereby thetimer piston cannot be controlled at the time of starting the engine.

Accordingly, at the time of starting the engine, the timer piston stillexists at the position at which the piston exists at the time that thestopping process is performed (that is, the above-mentioned position ofnormal driving of the engine).

However, it is generally known that the more the timing of fuelinjection is advanced, the more the start ability of an engine isimproved.

Accordingly, with regard to the conventional fuel injection system, thestart ability at the time of starting the engine is not necessarilygood, whereby actuation time of a starting motor is long so that theload applied on a battery is large.

There is conventionally known a fuel injection system which controlsdrivingly a fuel injection pump injecting fuel to a cylinder of a dieselengine, a hydraulic timer unit changing the phase of timing of fuelinjection, a governor adjusting fuel injection amount, and the like.

An example of such a conventional fuel injection system is described inthe patent literature 1.

With regard to such a fuel injection system, for example, position of arack provided within a governor is generally controlled drivinglyfollowing engine rotation speed or manifold pressure of a supercharger(turbocharger). The relation thereof has been memorized previously in anECM which is an example of a control means of the engine and the fuelinjection system, and an example of the relation is shown in FIG. 6.

With regard to a graph in FIG. 6, the axis of abscissas shows “enginerotation speed” and “manifold pressure” of the supercharger and the axisof ordinates shows “rack position”. The graph shows curves as describedbelow.

With regard to the relation between manifold pressure of thesupercharger and rack position, an intake rack position limit curve RTshows the relation between manifold pressure and rack position at whichthe fuel injection amount is maximized. So to speak, the curve is anupper limit line of the rack position.

With regard to the relation between engine rotation speed and rackposition, a rotation speed rack position limit curve RM shows therelation between engine rotation speed and rack position at which thefuel injection amount is maximized. So to speak, the curve is an upperlimit line of rack position.

With regard to the relation between engine rotation speed and rackposition, a rotation speed rack position minimum curve RS shows therelation between engine rotation speed and rack position at which thefuel injection amount is minimized. So to speak, the curve is a lowerlimit line of rack position.

Though the intake rack position limit curve RT does not depend directlyon engine rotation speed, the intake rack position limit curve RT andthe rotation speed rack position limit curve RM may have the same rackposition RC (point EC). Accordingly, based on the point EC, the intakerack position limit curve RT and the rotation speed rack position limitcurve RM can be shown in one graph.

Namely, the intake rack position limit curve RT can be drawn as if thecurve RT changes depending on engine rotation speed.

In addition, FIG. 6 shows an example of a fuel injection system of aship or the like.

Now, conventionally, the ECM selects one of the intake rack positionlimit curve RT and the rotation speed rack position limit curve RM asthe upper limit line of rack position as described below.

The ECM selects one of the lines, which makes the control range of rackposition narrower, as the upper limit line.

For example, in the case that the engine idles and rotation speed islow, that is, in the case that engine rotation speed is M1 and manifoldpressure is F1, the intake rack position limit curve RT, which makes thecontrol range of rack position narrower than the rotation speed rackposition limit curve RM, is selected as the upper limit line.

By this selection, the maximum fuel injection amount can be limited soas to suppress discharge of unburnt gas and black smoke.

Therefore, at the actual operation, the ECM selects the intake rackposition limit curve RT as the upper limit line in the case that theengine rotation speed is between M1 and MC for example. On the otherhand, the ECM selects the rotation speed rack position limit curve RM asthe upper limit line in the case that the engine rotation speed isbetween MC and M2.

Namely, a curve passing through a point ET1, a point EC and a point EM2is the upper limit line of rack position.

With regard to the above-mentioned fuel injection system, in the casethat fuel injection amount is adjusted based on engine rotation speed,for example, maximum fuel injection amount and minimum fuel injectionamount corresponding to engine rotation speed have been determinedpreviously, and fuel injection amount is adjusted within this range.Namely, in this case, the relation between engine rotation speed and themaximum fuel injection amount and the relation between engine rotationspeed and the minimum fuel injection amount have been memorizedpreviously in the control means such as the ECM of the fuel injectionsystem, and fuel injection amount is controlled based on theserelations.

Now, in the case that engine rotation speed is lower than thepredetermined minimum set rotation speed for improving enginefailure-proof ability or another reason, there is a fuel injectionsystem like the above mentioned controlling fuel injection amount to beincreased following a decrease of the engine rotation speed. Namely, inthe case that the engine rotation speed is the minimum set rotationspeed, such as the case of idling, when load is applied on the engine byengaging a clutch or the like, the engine rotation speed may becomelower than the minimum set rotation speed so as to cause engine failure.However, by increasing fuel injection amount following the fall ofengine rotation speed at the lower rotation side than the minimum setrotation speed, the engine failure is prevented.

With regard to such a fuel injection system, the relation between enginerotation speed and fuel injection amount for increasing the fuelinjection amount following the fall of the engine rotation speed at thelower rotation side than the minimum set rotation speed has beenmemorized in the control means corresponding to the certainpredetermined minimum set rotation speed as mentioned above.Accordingly, when the minimum set rotation speed is changed, belowdefects may be caused.

The minimum set rotation speed is the minimum rotation speed of therange adjustable by operating a throttle or the like and is the enginerotation speed at the time of idling normally. Accordingly, for examplein the case that the minimum set rotation speed is increased, when loadis applied on the engine by engaging a clutch or the like at the time ofidling, operability and driving feeling may be spoiled. The increase offuel injection amount following the fall of engine rotation speed at thelower rotation side than the minimum set rotation speed is based on therelation between engine rotation speed and fuel injection amountdetermined corresponding to the certain minimum set rotation speed.Accordingly, in the case that the minimum set rotation speed isincreased, the amount of fall of the engine rotation speed caused byapplying the load may be increased and the fall of the engine rotationspeed caused by applying the load may be not enough to increase fuelinjection amount sufficiently. When such a phenomenon occurs, therecovery of fall of engine rotation speed by applying the load requiresa measure of time, thereby spoiling operability and driving feeling.

To the contrary, in the case that the minimum set rotation speed isdecreased, unnecessary fuel may be injected excessively so as toincrease discharge of unburnt fuel.

Patent Literature 1: the Japanese Patent Laid Open Gazette 2004-218636

BRIEF SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The first purpose of the invention is to provide a fuel injection systemwhich improves the start ability of an engine.

The second purpose of the invention is to provide a fuel injectionsystem which prevents engine failure even if a load is applied at thetime that the engine rotation speed is low such as the time of idling.

The third purpose of the invention is to provide a fuel injectionsystem, constructed to increase the fuel injection amount following afall of the engine rotation speed at lower rotation side than a minimumset rotation speed, which maintains engine failure-proof ability andprevents a fall of operability and driving feeling and an increase ofdischarge of unburnt fuel accompanied by a change of the minimum setrotation speed.

Means for Solving the Problems

The above-mentioned problems are solved by the following means.

According to the present invention, with regard to a fuel injectionsystem comprising a control means controlling timing of fuel injectionto a cylinder of an engine, the control means advances the timing offuel injection so as to perform a stopping process of the engine whenthe stopping process is required.

Accordingly, at the time of stopping the engine, the timing of fuelinjection is stopped at the advanced angle side at which the startability of the engine is improved. Accordingly, the start ability isimproved at the time of starting the engine next so as to make startingtime of a starting motor shorter than the conventional construction,thereby reducing load on a battery.

The timing of fuel injection is changed by a timer piston.

Accordingly, the conventional timer piston can be used so as to reducecost.

The control means controls phase difference between a crankshaft of theengine and the timing of fuel injection to be not less than apredetermined phase difference in the case of advancing the timing offuel injection.

Accordingly, the phase difference at which the start ability is improvedcan be set in the control means concretely.

The control means performs the stopping process without advancing thetiming of the fuel injection in the case of stopping the engine in anemergency.

Accordingly, at the time that the emergency stopping of the engine isrequired because of abnormality of the engine or the like, the timing offuel injection is not advanced, whereby the engine can be stoppedemergently.

Furthermore, according to the present invention, with regard to a fuelinjection system comprising a rack which adjusts the fuel injectionamount of a fuel injection pump injecting fuel to an engine, and acontrol means which controls the rack based on an intake rack positionlimit curve determining relation between intake pressure of asupercharger and a rack position maximizing fuel injection amount or arotation speed rack position limit curve determining relation betweenengine rotation speed and the rack position maximizing fuel injectionamount, the control means has a curve selection means selecting one ofthe intake rack position limit curve and the rotation speed rackposition limit curve which makes the control range of the rack positionwider when engine rotation speed falls for not less than a predeterminedrotation speed from a target rotation speed.

Accordingly, one of the curves which makes the control range of the rackposition wider is selected when the rotation speed of the engine fallsfor not less than the predetermined rotation speed from the targetrotation speed, whereby the fuel injection amount is increasedpertinently so as to prevent engine failure.

According to the present invention, with regard to a fuel injectionsystem comprising a rack which adjusts the fuel injection amount of afuel injection pump injecting fuel to an engine, and a control meanswhich controls the rack based on an intake rack position limit curvedetermining relation between intake pressure of a supercharger and arack position maximizing a fuel injection amount or a rotation speedrack position limit curve determining the relation between enginerotation speed and the rack position maximizing fuel injection amount,the control means has a curve selection means selecting one of theintake rack position limit curve and the rotation speed rack positionlimit curve which makes the control range of the rack position widerwhen elapsed time from starting the engine is within a predeterminedrange.

Accordingly, one of the curves which makes the control range of the rackposition wider is selected within a range of a predetermined time fromthe starting of the engine, whereby a fuel injection amount is increasedpertinently so as to prevent engine failure.

Furthermore, according to the present invention, with regard to a fuelinjection system comprising a control means controlling a fuel injectionamount of a fuel injection pump based on a lower rotation speed sidefuel injection amount characteristic curve which determines the relationbetween engine rotation speed and fuel injection amount so that the fuelinjection amount is increased following a fall of the engine rotationspeed at a lower rotation side than changeable minimum set rotationspeed, the control means increases and decreases engine rotation speedcorresponding to fuel injection amount of the lower rotation speed sidefuel injection amount characteristic curve following an increase anddecrease of the minimum set rotation speed.

Accordingly, engine failure-proof ability is maintained and the fall ofoperability and driving feeling and an increase of discharge of unburntfuel accompanied by the change of the minimum set rotation speed isprevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of schematic construction of a fuel injectionsystem.

FIG. 2 is a drawing of a fuel injection pump and devices in connectiontherewith.

FIG. 3 is a diagram of relation beyond a crankshaft pulse, a camshaftpulse and a timing of fuel injection.

FIG. 4 is a flow chart of a course of process performed so as to stop anengine.

FIG. 5 is a diagram of relation beyond state of a key switch, actualphase difference, state of fuel injection and engine rotation speed.

FIG. 6 is a diagram of relation beyond a rack position at which fuelinjection amount is maximum or minimum, engine rotation speed and asupercharger.

FIG. 7 is a flow chart of a course of process for preventing an enginefailure.

FIG. 8 is a diagram of an example of change of relation between time andengine rotation speed at the time of starting engine.

FIG. 9 is a diagram of an example of change of relation between time andengine rotation speed at the time that the engine rotation speed falls.

FIG. 10 is a diagram of relation between engine rotation speed and fuelinjection amount.

FIG. 11 is a drawing of the same expanded partially.

DETAILED DESCRIPTION OF THE INVENTION

Explanation will be given on the best mode for carrying out the presentinvention in connection with the accompanying drawings for understandingthe present invention. In addition, the best mode for carrying out thepresent invention described below is a concrete example of the presentinvention and does not limit the technical extent of the presentinvention.

<Schematic Construction>

First, explanation will be given on the schematic construction of a fuelinjection system 1 of the present invention according to FIG. 1.

Here, explanation will be given on a case that that the fuel injectionsystem 1 is adopted as a control system of a fuel injection pumpprovided in a ship for example. However, the fuel injection system 1 maybe adopted to anything which can obtain the same effect by this system.

As shown in FIG. 1, the fuel injection system 1 broadly comprises anoperation part 10 and an engine 20.

The operation part 10 is provided in a driving cab of the ship and has adisplay part 11, a main throttle 12 and a sub throttle 13 for example.

The display part 11 displays the state of the ship to which the systemis adopted, cautions, and the like, and may give caution with voice byproviding a built-in speaker or the like.

The main throttle 12 is operated in the case that the ship is in normaldriving state and operates a throttle valve 29 of the engine 20. Forexample, the main throttle 12 is operated via a lever.

A key switch 12 a starting the engine 20 is provided in the operationpart 10 integrally with or separately from the main throttle 12.

The sub throttle 13 operates the throttle valve 29 similarly to the mainthrottle 12. However, differently from the main throttle 12, the subthrottle 13 is operated in the case that the ship is not in normaldriving state. For example, the sub throttle 13 is operated via a knob.

Each of the display part 11 and the main throttle 12 has an individualcontrol part and communicates with an ECM (Engine Control Module) 21 soas to control the operation part 10 and the engine 20 entirely.

In addition, when the communication mode such as a protocol differsbetween the operation part 10 and the engine 20, a communicationrepeater 15 is provided as shown in FIG. 1 so as to coordinate thecommunication mode.

The sub throttle 13 is connected directly to the ECM 21 of the engine 20and has the same communication mode as the engine 20.

The engine 20 is a diesel engine for example and comprises the ECM 21, acrankshaft rotation speed sensor 22, a camshaft rotation speed sensor23, a retarded angle electromagnetic valve 24, an advanced angleelectromagnetic valve 25, a manifold pressure sensor 27, a rack 28 andthe like.

The ECM 21 controls actuators and the like in connection with the engine20 based on the state of sensors in connection with the engine 20, theoperation system such as the above-mentioned operation part 10, and thelike.

The crankshaft rotation speed sensor 22 detects rotation speed of acrankshaft of the engine 20 and outputs the detected result as acrankshaft pulse to the ECM 21.

Namely, the rotation speed of the engine 20 can be detected by thecrankshaft rotation speed sensor 22.

The camshaft rotation speed sensor 23 detects rotation speed of acamshaft of the engine 20 and outputs the detected result as a camshaftpulse to the ECM 21.

The crankshaft rotation speed sensor 22 and the camshaft rotation speedsensor 23 may be constructed by optical sensors. For example, byproviding marks of prescribed numbers at prescribed intervals on thecrankshaft and the camshaft or gears thereof previously at the time ofmanufacture, the ECM 21 can calculate the rotation speeds of thecrankshaft and the camshaft 41 by detecting the marks by opticalsensors.

The retarded angle electromagnetic valve 24 and the advanced angleelectromagnetic valve 25 are oil pressure regulating valves whichcontrols oil pressure which slides a timer piston of a hydraulic timerunit, changing phase of a camshaft of a fuel injection pump 40 shown inFIG. 2, toward retarded or advanced side.

The manifold pressure sensor 27 detects manifold pressure of asupercharger provided on the engine 20.

The rack 28 adjusts the amount of fuel injected from the fuel injectionpump 40.

<Fuel Injection Pump>

Next, explanation will be given on the schematic construction of thefuel injection pump 40 and devices in connection therewith according toFIG. 2.

In addition, a hydraulic timer unit 50 in FIG. 2 is shown in section.

Especially, a timer piston 52 is divided into upper and lower portionsby an alternate long and short dash line for convenience. The piston atthe retarded position is shown by a timer piston 52 a, and the piston atthe advanced position is shown by a timer piston 52 b.

Of course, the actual timer piston 52 is not divided into two by thealternate long and short dash line and is formed integrally. In FIG. 2,the timer piston 52 is divided into two by the alternate long and shortdash line so as to explain the movement of the timer piston 52.

The fuel injection pump 40 pressingly sends fuel stored in a fuel tankto an injection nozzle provided in a cylinder of the engine 20 and isdriven by a camshaft 41. A coupling fixture 42 is fixed to the tip ofthe camshaft 41 so as to fix a camshaft coupling 51 to the camshaft 41.

Supply ports 43 of the same number as cylinders of the engine 20 areprovided in the fuel injection pump 40 so as to supply fuel to thecylinders. FIG. 2 shows the case that six cylinders are provided.

Furthermore, a governor 30 and the hydraulic timer unit 50 are providedintegrally with the fuel injection pump 40.

The governor 30 has the rack 28 and the rack 28 is driven by aproportional solenoid drivingly controlled by the ECM 21.

The timer piston 52, spline-fitting the outer peripheral surface of thecamshaft coupling 51 straightly, is provided in the hydraulic timer unit50. Moreover, a pump driving gear 53, spline-fitting the outerperipheral surface of the timer piston 52 helically, is provided in thehydraulic timer unit 50.

The pump driving gear 53 is fixed by a driven gear 55, receiving torquefrom the crankshaft of the engine 20, and a bolt 56.

According to the above-mentioned construction, the camshaft 41 can berotated by the rotation of the crankshaft. Furthermore, by sliding thetimer piston 52 along the spline direction of the camshaft coupling 51(lateral direction in FIG. 2), the phase difference between the camshaftcoupling 51 and the pump driving gear 53 can be changed.

In addition, as was previously mentioned, the helical shape of thespline fit is constructed so that the camshaft is retarded by slidingthe timer piston 52 toward the side of the piston 52 a, and is advancedby sliding the timer piston 52 toward the side of the piston 52 b.

A space made at the outer peripheral side of the timer piston 52 fittingthe pump driving gear 53 is referred to as a retarded angle chamber 57a, and a space made at the inner peripheral side of the timer piston 52fitting the camshaft coupling 51 is referred to as an advanced anglechamber 57 b.

In this case, the timer piston 52 can be slid toward the retarded angleside (the side of the piston 52 a) by pressingly sending pressure oil tothe retarded angle chamber 57 a, and the timer piston 52 can be slidtoward the advanced angle side (the side of the piston 52 b) bypressingly sending pressure oil to the advanced angle chamber 57 b.

The retarded angle electromagnetic valve 24 and the advanced angleelectromagnetic valve 25 are disposed in each of a retarded angle oilpassage 58 a connected to the retarded angle chamber 57 a and anadvanced angle oil passage 58 b connected to the advanced angle chamber57 b. The retarded angle electromagnetic valve 24 and the advanced angleelectromagnetic valve 25 are controlled and operated by the ECM 21 so asto send pressure oil, thereby sliding the timer piston 52.

According to the above-mentioned construction, the ECM 21 functions as acontrol means controlling the timer piston 52 by hydraulic pressureaccording to the state of the engine 20 so that the phase differencebetween the crankshaft of the engine 20 and the camshaft 41 can beretarded or advanced freely.

<Actual Phase Difference>

As was previously mentioned, the marks have been provided on thecrankshaft and the camshaft 41 or gears thereof previously and aredetected by the crankshaft rotation speed sensor 22 and the camshaftrotation speed sensor 23. Based on the crankshaft pulse and the camshaftpulse which are the detected results, the ECM 21 calculates the rotationspeeds of the crankshaft and the camshaft 41.

Accordingly, based on the difference between the detected times of thecrankshaft pulse and the camshaft pulse, the ECM 21 also can calculatethe phase difference between the crankshaft and the camshaft.

Then, explanation will be given on relation beyond the crankshaft pulse,the camshaft pulse and the actual timing of fuel injection according toFIG. 3.

FIG. 3 shows the relation beyond crankshaft pulses J1, J2 and J3, theactual timing of fuel injection of certain supply port 43 (hereinafter,referred to as “FIC”), and a camshaft pulse T2 corresponding to the FIC.

In addition, FIG. 3 (a) shows the relation of the detection time ofpulse (phase difference) in the case that the camshaft 41 is advancedagainst the crankshaft, and FIG. 3 (b) shows the relation of thedetection time of pulse (phase difference) in the case that the camshaft41 is retarded against the crankshaft.

As shown in FIG. 3, for example, the crankshaft pulses J1, J2 and J3correspond to the marks provided on the crankshaft previously so as tobe detected every 30 [deg].

The phase of the camshaft pulse T2 is obtained by calculating an angle Bwhich is a phase difference against the crankshaft pulse J2corresponding to the camshaft pulse T2.

Now, when the fuel injection is actually performed at the phase of thecamshaft pulse T2, the angle B is the phase difference between thetiming of fuel injection and the crankshaft. However, in the embodimentshown in FIG. 3, on the convenience of the design of the hydraulic timerunit 50, the fuel injection pump 40 and the like, the camshaft pulse T2is not in agreement with the FIC and the FIC is shifted from thecamshaft pulse T2 for 10 [deg] in angle.

Namely, the phase of the actual timing of fuel injection is earlier thanthe timing of detection of the camshaft pulse T2 for equivalent of theangle of 10 [deg] in time.

Then, in consideration of the above-mentioned gap of 10 [deg], the ECM21 finally calculates the phase difference between the FIC and thecrankshaft pulse J2 as “actual phase difference C”.

Namely, the phase difference C is the phase difference between thetiming of fuel injection, determined by the camshaft 41, and thecrankshaft.

<Calculation of Actual Phase Difference C>

Next, explanation will be given on a method for calculating the actualphase difference C against the crankshaft pulse J2.

Firstly, the ECM 21 measures the time from the detection of thecrankshaft pulse J1 just before the crankshaft pulse J2 to the detectionof the camshaft pulse T2, and calculates the phase differencecorresponding to the measured time as an angle A.

Then, the ECM 21 calculates the remainder of the angle of 30 [deg],which is the predetermined phase difference between the crankshaft pulseJ1 and the crankshaft pulse J2, and the angle A as the angle B.

Namely, the calculation “(30−A)=B” is performed.

The angle B is the phase difference between the crankshaft pulse J2 andthe camshaft pulse T2. Accordingly, the ECM 21 adds the predeterminedphase difference between the camshaft pulse T2 and the FIC (theabove-mentioned angle of 10 [deg]) to the angle B so as to calculate theactual phase difference C.

Namely, the calculation “B+10” is performed.

By performing the detection of the pulses and the calculation process asmentioned above, the actual phase difference C can be calculated.

In addition, the ECM 21 discriminates the crankshaft pulse J2 from thecrankshaft pulse J1 by the way discussed below.

For example, a mark is provided close to the crankshaft pulse J2 at aninterval not larger than 30 [deg] so as to detect a reset pulse JX.

By providing the mark corresponding to the reset pulse JX, when the ECM21 detects two pulses at an interval smaller than 30 [deg] which is theangle of the interval between the crankshaft pulses, the first detectedpulse can be recognized as the crankshaft pulse J2.

The ECM 21 changes the actual phase difference C, calculated asmentioned above, corresponding to the state of the engine 20 so as todetermine the timing of fuel injection suitable to the state of theengine 20.

<Flow of Process>

Now, with regard to the conventional fuel injection system, when anoperation stopping an engine is performed, a timer piston is stopped ata position at which the piston exists at the time that an operatorperforms the stopping operation.

Accordingly, at the time of starting the engine, the timer piston stillexists at the position of the stopping operation. Therefore, theconventional fuel injection system is not necessarily excellent in startability.

Then, explanation will be given on a course of process solving theabove-mentioned problem according to a flow chart shown in FIG. 4.

Also, explanation will be given on an example of change of operationstatus of the key switch 12 a, the actual phase difference C, the stateof injection of fuel, the rotation speed of the engine 20 and the likein the stopping operation according to FIG. 5.

In addition, FIG. 5 (a) shows the ON/OFF operation status of the keyswitch 12 a. FIG. 5 (b) shows temporal change of the actual phasedifference C as an actual phase difference curve L. FIG. 5 (c) shows thestate of injection of fuel by the fuel injection pump 40. FIG. 5 (d)shows the rotation speed of the engine 20.

Firstly, the ECM 21 drives the engine 20 normally (S10).

At this time, each part of the fuel injection system 1 is in the statebefore time U1 in FIG. 5. The key switch 12 a and the fuel injection areturned on, the actual phase difference C fluctuates slightly temporally,and the engine 20 is driven at rotation speed Y.

Next, the ECM 21 judges whether a request of the stopping process of theengine 20 exists or not (S12).

This process is performed by, for example, judging whether an operatorturns the key switch 12 a off so as to request the stopping process ofthe engine 20 or not.

When the request of the stopping process is judged to exist by thisprocess, the process is shifted to a step S14. On the other hand, whenthe request of the stopping process is judged not to exist, the processof the step S12 is repeated.

When the request of the stopping process of the engine 20 exists, theECM 21 makes the timer piston 52 move toward the advanced angle side(S14).

Namely, the ECM 21 advances the timing of fuel injection.

At this time, the actual phase difference C changes from the time U1 asshown in the actual phase difference curve L in FIG. 5 (b), and thevalue of the actual phase difference C becomes large gradually. Namely,the actual phase difference C is changed toward the advanced angle side.

Then, at time U2, the actual phase difference C reaches a predeterminedphase difference at which the engine 20 is stopped (that is, stoppingtarget phase difference Z).

The stopping target phase difference Z is an example of phase differencesuitable to improve the start ability of the engine 20 and has beenstored in the ECM 21 previously.

After the process of the step S14, the ECM 21 judges whether the actualphase difference C reaches the stopping target phase difference Z or not(S16).

Namely, the ECM 21 judges whether the actual phase difference C becomesnot less than the stopping target phase difference Z or not.

Then, the ECM 21 stops the fuel injection to the cylinder of the engine20 (S18).

This process can be performed, for example, by a way that the ECM 21closes the rack 28, the electromagnetic valve in the fuel injection pump40 or the fuel supply electromagnetic valve to the fuel injection pump40.

By the process of the step S18, the stopping process of the engine 20 isperformed.

For example, when the fuel injection is stopped at the time U2 as shownin FIG. 5, engine rotation speed begins to be reduced, and finallyengine rotation speed becomes 0 and the engine is stopped at time U3.

By controlling as mentioned above, at the time of stopping the engine20, the timing of fuel injection is stopped at the advanced angle sideat which the start ability of the engine 20 is improved. Accordingly,the start ability is improved at the time of starting the engine 20 nextso as to make starting time of a starting motor shorter than theconventional construction, thereby reducing load on a battery.

The ECM 21 controls the phase difference between the timing of fuelinjection and the crankshaft of the engine 20 to be not less than thestopping target phase difference Z. Accordingly, the phase difference atwhich the start ability is improved can be set in the ECM 21 concretely.

<Case of Emergency Stopping of Engine 20>

The above-mentioned course of process (the process from the step S12 tothe step S18) may be set not to be performed at the time that theemergency stopping of the engine 20 is required because of abnormality,such as breaking of wire or short circuit, of the engine 20, thehydraulic timer unit 50, the operation part 10, the communicationrepeater 15 or a connecting harness.

That is because the stopping needs a long time if the above-mentionedcourse of process is performed although the abnormality occurs and theemergency stopping is required.

Then, by processing as mentioned above, the engine 20 can be stoppedemergently when the abnormality occurs.

<Engine Failure Preventing Process>

Now, as explained according to FIG. 6 previously, the rack position atwhich the fuel injection amount becomes the maximum (upper limit line)is determined by an intake rack position limit curve RT or a rotationspeed rack position limit curve RM previously memorized in the ECM 21.

Then, corresponding to rotation speed of the engine 20 and intakepressure of the supercharger, one of the curves are selected as theupper limit line so as to make the control range of the rack positionnarrower.

Accordingly, the maximum fuel injection amount is limited so that suddendecline of the engine rotation speed caused by applying a load or thelike may not be dealt with, thereby causing engine failure.

Therefore, explanation will be given on a course of process preventingengine failure in such a case that mentioned above according to FIG. 7.

<Starting Engine>

First, when the engine 20 is started by operating the key switch 12 a,the ECM 21 judges whether elapsed time after starting the engine 20 iswithin the range of predetermined time or not (S20).

The predetermined time has been memorized in the ECM 21 or the likepreviously and is about 2 seconds.

Namely, the ECM 21 judges whether the elapsed time after the starting isnot more than 2 seconds or not at the process of the step S20.

At the process of the step S20, when the elapsed time after starting theengine 20 is judged to be within the range of predetermined time, theprocess is shifted to a step S30. On the other hand, when the elapsedtime is judged not to be within the range, the process is shifted to astep S22.

When the process is shifted to the step S30, the engine 20 isimmediately after the starting and is idled, whereby the engine rotationspeed is between M1 and MC in FIG. 6.

In this case, the control range of the rack position becomes wider byselecting the rotation speed rack position limit curve RM compared withthe rack position limit curve RT. Accordingly, the ECM 21 selects therotation speed rack position limit curve RM as the upper limit linedetermining the rack position at which the fuel injection amount becomesthe maximum (S30).

Namely, the ECM 21 also functions as an example of a curve selectionmeans selecting one of the rack position limit curve RT and the rotationspeed rack position limit curve RM which makes the control range of therack position wider.

Here, explanation will be given on an example of change of relationbetween time and engine rotation speed in the case that the process isshifted from the step S20 to the step S30 according to FIG. 8.

In addition, time U4, conventional engine rotation speed curve MM andprocessed engine rotation speed curve MA2 shown in FIG. 8 have belowmeans.

The time U4 is the time at which the engine 20 is started.

The conventional engine rotation speed curve MA1 shows a temporal changeof the engine rotation speed in the case of selecting the curve whichmakes the control range of the rack position narrower conventionally.

The processed engine rotation speed curve MA2 shows a temporal change ofthe engine rotation speed in the case that the process from the step S20to the step S30 is performed and the curve which makes the control rangeof the rack position wider is selected.

In this case, just after the engine 20 has been started at the time U4,the processed engine rotation speed curve MA2 is larger than theconventional engine rotation speed curve MA1.

Namely, though the conventional engine rotation speed curve MA1 remainsnear engine rotation speed M5 until time U5, the processed enginerotation speed curve MA2 reaches engine rotation speed M6 larger thanthe engine rotation speed M5 just after the time U4 and indicates enoughoutput.

The range of predetermined time of the step S20 is between the time U4and time U6 for example, and the rotation speed rack position limitcurve RM is selected as the upper limit line within the range.

Accordingly, by performing the process from the step S20 to the stepS30, the rotation speed rack position limit curve RM which makes thecontrol range of the rack position wider is selected within the range ofa predetermined time from the starting of the engine 20, whereby fuelinjection amount is increased pertinently so as to prevent enginefailure.

<Not More than Predetermined Rotation Speed>

When the process is shifted to the step S22, the ECM 21 judges whetherthe rotation speed of the engine 20 falls for not less than thepredetermined rotation speed from the target rotation speed (S22).

The predetermined rotation speed has been memorized in the ECM 21 or thelike previously and is about 50 revolutions.

At the process of the step S22, when the rotation speed of the engine 20is judged to fall for not less than the predetermined rotation speedfrom the target rotation speed, the process is shifted to a step S30. Onthe other hand, when the rotation speed is judged not to fall, theprocess is shifted to a step S40.

Here, explanation will be given on an example of a change of therelation between time and engine rotation speed in the case that theprocess is shifted from the step S22 to the step S30 and engine rotationspeed falls according to FIG. 9.

In addition, time U8, conventional engine rotation speed curve MA3 andprocessed engine rotation speed curve MA4 shown in FIG. 9 have belowmeans.

The time U8 is the time at which rotation speed of the engine 20 becomeslower than the target rotation speed.

The conventional engine rotation speed curve MA3 shows a temporal changeof the engine rotation speed in the case of selecting the curve whichmakes the control range of the rack position narrower conventionally.

The processed engine rotation speed curve MA4 shows a temporal change ofthe engine rotation speed in the case that the process from the step S22to the step S30 is performed and the curve which makes the control rangeof the rack position wider is selected.

As shown in FIG. 9, when the engine rotation speed becomes lower thanthe target rotation speed M10, the processed engine rotation speed curveMA4 is higher than the conventional engine rotation speed curve MA3 andalso returns to the target rotation speed M10 sooner.

Namely, though the conventional engine rotation speed curve MA3 reachesengine rotation speed M9 widely lower than the target rotation speed M10at time U9, the processed engine rotation speed curve MA4 turns atengine rotation speed M11 higher than the engine rotation speed M9before the time U9 and returns to the target rotation speed M10.

The range of predetermined rotation speed of the step S22 is between thetarget rotation speed M10 and engine rotation speed M8 for example, andthe rotation speed rack position limit curve RM is selected as the upperlimit line while the engine rotation speed is less than the enginerotation speed M8.

Accordingly, by performing the process from the step S22 to the stepS30, the rotation speed rack position limit curve RM which makes thecontrol range of the rack position wider is selected when the rotationspeed of the engine 20 falls for not less than the predeterminedrotation speed from the target rotation speed, whereby fuel injectionamount is increased pertinently so as to prevent engine failure.

<Normal Control>

When the process is shifted to the step S40, normal control which hasbeen used conventionally is preformed.

Namely, the ECM 21 controls so that one of the intake rack positionlimit curve RT and the rotation speed rack position limit curve RM whichmakes the control range of the rack position narrower is selected as therack position at which fuel injection amount becomes the maximum (upperlimit line).

<Control of Fuel Injection Amount>

With regard to the fuel injection system 1 constructed as mentionedabove, the fuel injection amount of the fuel injection pump 40, that is,the position of the rack 28 in the governor 30 in this embodiment(hereinafter, simply referred to as “rack position”) is adjusted basedon the rotation speed of the engine 20 (hereinafter, simply referred toas “engine rotation speed”) and the intake pressure of the supercharger.Namely, driving of the rack 28, whose position is adjusted so as toadjust the fuel injection amount, is controlled corresponding to theengine rotation speed and the intake pressure of the supercharger, andthe relation beyond them has been memorized in the ECM 21 which is anexample of the memory means previously.

The relation between engine rotation speed and fuel injection amount(rack position) is concretely shown in a graph in FIG. 10. Namely, withregard to the fuel injection system 1 according to the presentinvention, the fuel injection amount against the engine rotation speedis controlled based on a maximum fuel injection amount characteristiccurve F (hereinafter, simply referred to as “maximum characteristiccurve F”) determining the relation between engine rotation speed andmaximum fuel injection amount and a minimum fuel injection amountcharacteristic curve G (hereinafter, simply referred to as “minimumcharacteristic curve G”) determining the relation between enginerotation speed and minimum fuel injection amount.

Then, based on a lower rotation speed side fuel injection amountcharacteristic curve (hereinafter, simply referred to as “lower rotationspeed side characteristic curve”) g which determines the relationbetween engine rotation speed and fuel injection amount and increasesfuel injection amount following decrease of engine rotation speed at theside of lower rotation speed than minimum set rotation speed No whosesetting can be changed, the ECM 21 controls fuel injection amount of thefuel injection pump at the side of lower rotation speed than the minimumset rotation speed No.

The maximum characteristic curve F shows the maximum fuel injectionamount calculated based on each engine rotation speed with regard to therelation between engine rotation speed and fuel injection amount, and isan upper limit line of the fuel injection amount so to speak.

The minimum characteristic curve G shows minimum fuel injection amountcalculated based on each engine rotation speed with regard to therelation between engine rotation speed and fuel injection amount, and isa lower limit line of the fuel injection amount so to speak.

The minimum set rotation speed No is the minimum engine rotation speedwithin the range of rotation speed adjustable by operating the mainthrottle 12 or the like, and is the engine rotation speed at the normalidling and has been set by the ECM 21 previously. In addition, in thegraph in FIG. 10, a sign Nm indicates the maximum set rotation speed.The maximum set rotation speed Nm is maximum engine rotation speedwithin the range of rotation speed adjustable by operating the mainthrottle 12 or the like and has been set by the ECM 21 previously.

As was previously mentioned, when the engine rotation speed is lowerthan the minimum set rotation speed No, the ECM 21 controls the fuelinjection amount based on the lower rotation speed side characteristiccurve g. The lower rotation speed side characteristic curve g shows apart of the lower rotation speed side of the minimum characteristiccurve G, and shows the fuel injection amount characteristic increasingthe fuel injection amount following a decrease of the engine rotationspeed when engine rotation speed is lower than the minimum set rotationspeed No.

As shown in FIG. 10, the lower rotation speed side characteristic curveg has an intersection point X at which the curve g intersects themaximum characteristic curve F concerning engine rotation speed lowerthan the minimum set rotation speed No. At the side lower than theintersection point X, the fuel injection amount is increased higher thanthe value determined by the maximum characteristic curve F.

Namely, the ECM 21 fundamentally controls the fuel injection amount byadjusting rack position corresponding to load or the like within therange between the maximum characteristic curve F and the minimumcharacteristic curve G including the lower rotation speed sidecharacteristic curve g. At the lower side of engine rotation speed, theECM 21 performs the control conforming to the lower rotation speed sidecharacteristic curve g so as to increase fuel injection amount followingdecrease of engine rotation speed. In this case, at the side lower thancertain engine rotation speed at the side lower than the minimum setrotation speed No (the engine rotation speed at the intersection pointX), fuel injection amount is increased along the lower rotation speedside characteristic curve g.

Accordingly, with regard to the fuel injection system 1 according to thepresent invention, the fuel injection amount is increased following adecrease of the engine rotation speed at the side lower than the minimumset rotation speed No set previously so as to improve enginefailure-proof ability. Namely, when engine rotation speed is decreasedat the time of applying load such as engaging the clutch while drivingat the minimum set rotation speed No such as idling, the fuel injectionamount is increased following a decrease of the engine rotation speed soas to prevent engine failure.

<Set of Minimum Set Rotation Speed>

For the purpose to improve the flexibility of the engine 20 and toprevent noise caused by resonance, the fuel injection system 1 isconstructed so that the minimum set rotation speed No can be changed.Namely, by changing the minimum set rotation speed No, the enginerotation speed at the time of idling can be changed so as to deal withdriving state desired by an operator. By enabling to change the minimumset rotation speed No at the time of idling, the resonance caused by theidling of the ship can be prevented, whereby noise caused by theresonance accompanied by the driving of the engine 20.

The minimum set rotation speed No is fundamentally set at the time ofdelivery of the fuel injection system 1. However, an operator can changethe minimum set rotation speed No with an operating panel provided inthe operation part 10 or the like. Concretely, for example, the minimumset rotation speed No can be changed within a range from 700 to 800[rpm] for every 20 [rpm].

With regard to the fuel injection system 1 constructed that the minimumset rotation speed No can be changed, the ECM 21 as a control meansincreases and decreases engine rotation speed, which corresponds to thefuel injection amount of the lower rotation speed side characteristiccurve g, following increase and decrease of the minimum set rotationspeed No by the change.

Namely, when the minimum set rotation speed is changed toward the higherrotation speed side so as to be increased from No to No 1 for example,the ECM 21 increases corresponding engine rotation speed of the lowerrotation speed side characteristic curve g following the increase of theminimum set rotation speed. In this case, on the graph in FIG. 10, thelower rotation speed side characteristic curve g of the minimumcharacteristic curve G is moved substantially horizontally toward thehigher rotation speed side (the right side) (see g1). To the contrary,when the minimum set rotation speed is changed toward the lower rotationspeed side so as to be decreased from No to No2, the ECM 21 decreasesthe corresponding engine rotation speed of the lower rotation speed sidecharacteristic curve g following the decrease of the minimum setrotation speed. In this case, on said graph, the lower rotation speedside characteristic curve g of the minimum characteristic curve G ismoved substantially horizontally toward the lower rotation speed side(the left side) (see g2).

Here, when the minimum set rotation speed No is increased or decreasedby the above-mentioned change of setting, the engine rotation speedcorresponding to fuel injection amount of the lower rotation speed sidecharacteristic curve g is increased or decreased following the increaseor decrease of the minimum set rotation speed No. However, the enginerotation speed corresponding to the fuel injection amount of the lowerrotation speed side characteristic curve g is not always increased ordecreased and the fuel injection amount characteristic may be changedfollowing the minimum set rotation speed No. Namely, the lower rotationspeed side characteristic curve g is not always moved substantiallyhorizontally on the graph while keeping its shape and the shape of thecurve may be changed following the change of the minimum set rotationspeed No. Otherwise, it may alternatively be constructed that plurallower rotation speed side characteristic curves g, corresponding torespective minimum set rotation speeds No settable within thepredetermined range of engine rotation speed, have been memorized in theECM 21 previously, and fuel injection amount is controlled based on thelower rotation speed side characteristic curve g corresponding to theminimum set rotation speed No set by an operator or the like.

Engine rotation speed corresponding to the fuel injection amount of thelower rotation speed side characteristic curve g is increased ordecreased following the change of the minimum set rotation speed No,thereby maintaining engine failure-proof ability and preventing a fallof the operability and driving feeling and an increase of discharge ofunburnt fuel accompanied by the change of the minimum set rotation speedNo.

Namely, in the case that the minimum set rotation speed No is increased,when load is applied at the time of idling or the like, the fuelinjection amount is increased pertinently following fall of enginerotation speed. Accordingly, the amount of fall of engine rotation speedis prevented from increasing so as to prevent fall of operability anddriving feeling. In the case that the minimum set rotation speed No isdecreased, excessive fuel injection is prevented at the time of idlingor the like, whereby increase of discharge of unburnt fuel is prevented.

<Effect of Control>

According to a partially expanded graph in FIG. 11, a concreteembodiment of change of engine rotation speed and fuel injection amountwill be shown and the above-mentioned effect is explained. Herein, theminimum set rotation speed before changed is referred to as No and thelower rotation speed side characteristic curve corresponding to theminimum set rotation speed No is referred to as g.

First of all, explanation will be given on the case that the minimum setrotation speed No is increased to No1.

First, it is supposed that the engine rotation speed corresponding tothe fuel injection amount of the lower rotation speed sidecharacteristic curve g is not increased (the lower rotation speed sidecharacteristic curve g is not moved) though the minimum set rotationspeed is increased from No to No1 and idling drive is performed whilethe engine rotation speed is the minimum set rotation speed No1. Namely,on the graph, this state corresponds to a point p1 at which enginerotation speed on the lower rotation speed side characteristic curve gis No1. In this state, when load is applied on the engine 20 by engagingthe clutch or the like, the fuel injection amount is increased to themaximum corresponding to the engine rotation speed at this state (No1).Namely, on the graph, the state is moved from the point p1 to a point p2on the maximum characteristic curve F. Since the engine rotation speedis decreased by the applied load, the state is moved from the point p2toward the lower rotation side along the maximum characteristic curve F.

Then, when the engine rotation speed falls to a certain value, the fuelinjection amount is increased based on the lower rotation speed sidecharacteristic curve g at the lower rotation side than the certainvalue. Namely, on the graph, when the state reaches from the point p2 tothe intersection point X of the maximum characteristic curve F and thelower rotation speed side characteristic curve g, fuel injection amountis increased based on the lower rotation speed side characteristic curveg at the lower rotation side than the engine rotation speed at theintersection point X. Subsequently, when the load is canceled, theengine rotation speed is increased and returns to the minimum setrotation speed No1, whereby the state corresponds to the point p1.

Namely, supposing that the engine rotation speed corresponding to thefuel injection amount of the lower rotation speed side characteristiccurve g is not increased (the lower rotation speed side characteristiccurve g is not moved) though the minimum set rotation speed is increasedfrom No to No1, when the engine rotation speed falls at the time ofidling, the engine rotation speed falls from No1 to the engine rotationspeed at the intersection point X until fuel injection amount exceedsthe injection amount based on the maximum characteristic curve F andincreased based on the lower rotation speed side characteristic curve g.

On the other hand, according to the present invention, it is supposedthat engine rotation speed corresponding to the fuel injection amount ofthe lower rotation speed side characteristic curve g is increasedfollowing increase of the minimum set rotation speed from No to No1 andidling drive is performed while engine rotation speed is the minimum setrotation speed No1. Namely, by increasing the minimum set rotation speedfrom No to No1, the lower rotation speed side characteristic curve g ismoved to g1, and the state corresponds to a point p3 at which enginerotation speed on the lower rotation speed side characteristic curve g1after moved is No1. From this state, when a load is applied on theengine 20 by engaging the clutch or the like, the fuel injection amountis increased similarly to the above-mentioned case and the state ismoved from the point p3 to the point p2 on the maximum characteristiccurve F. Subsequently, the engine rotation speed falls by the appliedload and the state is moved from the point p2 toward the lower rotationside along the maximum characteristic curve F.

Then, when the engine rotation speed falls to a certain value, the fuelinjection amount is increased based on the lower rotation speed sidecharacteristic curve g1 at the lower rotation side than the certainvalue. Namely, on the graph, when the state reaches from the point p2 toa intersection point X1 of the maximum characteristic curve F and thelower rotation speed side characteristic curve g1, the fuel injectionamount is increased based on the lower rotation speed sidecharacteristic curve g1 at the lower rotation side than the enginerotation speed at the intersection point X1. Subsequently, when the loadis canceled, the engine rotation speed is increased and returns to theminimum set rotation speed No1, whereby the state corresponds to thepoint p3.

Namely, since the lower rotation speed side characteristic curve g ismoved to g1 by increasing the minimum set rotation speed from No to No1,the engine rotation speed corresponding to the fuel injection amount ofthe lower rotation speed side characteristic curve g is increased andmoved to the lower rotation speed side characteristic curve g1.Accordingly, when the engine rotation speed falls at the time of idling,the engine rotation speed falls from No1 to the engine rotation speed atthe intersection point X1 until fuel injection amount exceeds theinjection amount based on the maximum characteristic curve F andincreased based on the lower rotation speed side characteristic curveg1.

Comparing these cases with each other, when the engine rotation speedfalls by applying a load at the time of idling at the minimum setrotation speed No1 after changed, the engine rotation speed falls fromNo1 to the engine rotation speed at the intersection point X until fuelinjection amount is increased based on the lower rotation speed sidecharacteristic curve g (or g1). However, the lower rotation speed sidecharacteristic curve g is moved to g1 so that the fall of enginerotation speed is suppressed to the engine rotation speed at theintersection point X1. Namely, the amount of fall of the engine rotationspeed is reduced for a remainder ΔN of the engine rotation speed at theintersection point X and the engine rotation speed at the intersectionpoint X1. In other words, the fall of engine rotation speed by applyingload is recovered faster for the remainder ΔN. Accordingly, fall ofoperability and driving feeling by applying load at the time of idlingis prevented.

Next, explanation will be given on the case that the minimum setrotation speed No is decreased to No2.

In this case, it is supposed that the engine rotation speedcorresponding to the fuel injection amount of the lower rotation speedside characteristic curve g is not increased (the lower rotation speedside characteristic curve g is not moved) though the minimum setrotation speed is increased from No to No2. Then, a point p4, at whichthe engine rotation speed on the lower rotation speed sidecharacteristic curve g is No2, corresponds to the idling while enginerotation speed is the minimum set rotation speed No2. Fuel injectionamount at this state is referred to as F0.

On the other hand, according to the present invention, it is supposedthat the engine rotation speed corresponding to the fuel injectionamount of the lower rotation speed side characteristic curve g isincreased following decrease of the minimum set rotation speed from Noto No2 so that the lower rotation speed side characteristic curve g ismoved to g2. Then, a point p5, at which the engine rotation speed on thelower rotation speed side characteristic curve g2 is No2, corresponds tothe idling while engine rotation speed is the minimum set rotation speedNo2. The fuel injection amount at this state is referred to as F2.

Namely, comparing these cases with each other, the engine rotation speedcorresponding to the fuel injection amount of the lower rotation speedside characteristic curve g falls following decrease of the minimum setrotation speed No, and the lower rotation speed side characteristiccurve g is moved to g2, whereby fuel injection amount at the minimum setrotation speed No2 after changed is decreased from F0 to F2.Accordingly, excessive fuel injection is prevented, whereby an increaseof discharge of unburnt fuel is prevented.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a fuel injection system of adiesel engine widely so as to improve start ability of the engine, toprevent engine failure and to prevent a fall of operability and drivingfeeling and an increase of discharge of unburnt fuel accompanied by achange of minimum set rotation speed.

1. A fuel injection system comprising: a control means controllingtiming of fuel injection to a cylinder of an engine, wherein, when theengine is required to stop, the control means advances the timing offuel injection so as to increase an actual phase difference between thetiming of fuel injection and rotation of a crankshaft of the engine,compares the actual phase difference with a target phase differencepredetermined for engine stopping, and stops the fuel injection afterthe control means judges that the increased actual phase difference hasreached the target phase difference.
 2. The fuel injection system as setforth in claim 1, wherein the timing of fuel injection is changed by atimer piston.
 3. The fuel injection system as set forth in claim 1,wherein the control means stops fuel injection without advancing thetiming of fuel injection in a case of stopping the engine emergently. 4.A fuel injection system comprising: a rack which adjusts fuel injectionamount of a fuel injection pump injecting fuel to an engine; and acontrol means configured to control the rack based on either (1) anintake rack position limit curve determining relation between intakepressure of a supercharger and a rack position maximizing fuel injectionamount or (2) a rotation speed rack position limit curve determiningrelation between engine rotation speed and the rack position maximizingfuel injection amount, wherein the control means has a curve selectionmeans selecting one of the intake rack position limit curve and therotation speed rack position limit curve which makes the control rangeof the rack position wider when engine rotation speed falls for not lessthan predetermined rotation speed from target rotation speed.
 5. A fuelinjection system comprising: a rack which adjusts fuel injection amountof a fuel injection pump injecting fuel to an engine; and a controlmeans configured to control the rack based on either (1) an intake rackposition limit curve determining relation between intake pressure of asupercharger and a rack position maximizing fuel injection amount or (2)a rotation speed rack position limit curve determining relation betweenengine rotation speed and the rack position maximizing fuel injectionamount, wherein the control means has a curve selection means selectingone of the intake rack position limit curve and the rotation rackposition limit curve which makes the control range of the rack positionwider when elapsed time from starting the engine is within apredetermined range.
 6. A fuel injection system comprising a controlmeans controlling fuel injection amount of a fuel injection pump basedon a lower rotation speed side fuel injection amount characteristiccurve which determines relation between engine rotation speed and fuelinjection amount so that fuel injection amount is increased followingfall of engine rotation speed at slower rotation side than changeableminimum set rotation speed, wherein the control means increases anddecreases engine rotation speed so as to correspond to fuel injectionamount of the lower rotation speed side fuel injection amountcharacteristic curve following increase and decrease of the minimum setrotation speed.